That creates a new directory for your app, pulls down a (sort of) minimal Gemfile, and then tells the bundler to bundle up Rails and all its dependencies for you to use in this app.

Then you’ll want to use the copy of Rails that you just bundled to generate the default app structure, like so:

./bin/rails .

When it asks you if you want to overwrite the Gemfile, you know what to do: just say n, kids.

After you’re done, I suggest running ./script/about to make sure that all the bundling went well and Rails can load and all that good stuff. Assuming it works, you have yourself a new Rails 3 app! And without installing any system gems. How about that.

Gems and generators and ooh shiny

At this point, you are pretty much set, and can run off and make your app do whatever it is that your heart desires. However, there are some more cool edgy things available, should you be interested. My current set of goodies includes Rack::Bug, Thor, RSpec, DataMapper, respondto scaffolds. Most of these goodies were inspired (or just copied) from github.com/josevalim/thirdrails.

To get their gems installed, uncomment the lines in the Gemfile and the run gem bundle again to install them all.

Because ActionView#render_templates has been removed, I had to comment out the TemplatesPanel in rack/bug/options.rb:80 for rack-bug to work. I imagine the bug will be fixed relatively quickly, though.

Git it done already

This is probably a good time to start tracking your app in source control:

TextMate with Rspec Bundle

Lastly, if you want to use RSpec from TextMate in the manner to which you have (likely) become accustomed, you will need to install a new version of RSpec.tmbundle that has support for libraries installed via the bundler.

Phew.

If you’ve actually made it all the way here, I’m terribly impressed. If for some reason you want to follow along with these steps, you can check out my blank Rails 3 app repository at Github. Have fun with Rails 3!